In the United States and throughout the world, there is increasing concern about the quality of air, particularly in large metropolitan areas. Air pollution is a significant problem in many metropolitan areas in the United States, such as Los Angeles, Calif., and in other large cities of the world, such as Bangkok, Kathmandu and Mexico City. It generally is agreed that a significant contributor to air pollution, particularly in large cities, is the internal combustion engine which is used in most automobiles and trucks. Such engines emit carbon monoxide and volatile unburned hydrocarbons, along with nitrogen oxide emissions. Substantial gains have been made in reducing the pollutants from internal combustion engines; but the ideal solution to the problem generally is conceded to be the utilization of electric vehicles, either battery powered, hybrid vehicles (those combining small internal combustion engines with electric motors and electric storage devices), or electric vehicles powered by fuel cells which burn hydrogen to generate electricity for operating an electric vehicle.
Electric drive vehicles, particularly battery-driven vehicles the wheels of which are turned by electric motors, have been known for as long as the internal combustion engine. Such vehicles, however, have never achieved a high degree of popularity, primarily because of the large weight and volume which is required by the batteries and the relatively short ranges which can be attained by such vehicles between battery charges. Electric vehicles currently on the market generally rely on lead-acid batteries charged from a standard wall plug. Lead-acid batteries are bulky and expensive; and in most practical applications they cannot drive a car over two hundred miles between charges. In most cases, the range between charges is even less than this. Electric vehicles using nickel-metal hydride batteries are capable of approximately doubling the range between charges for such electric vehicles. Nickel-metal hydride batteries, however, are extremely expensive, to the point that electric cars using such batteries essentially are impractical.
Even though battery driven electric vehicles currently (and for the foreseeable future) have a relatively limited range between chargings, the range which is available is one which is sufficient for a large number of city driving applications, particularly for a second or back-up vehicle. In addition, the ease of recharging the batteries from a wall outlet at home is a significant advantage for many users, since it eliminates the necessity of a trip to a refueling station, such as is required by gasoline powered vehicles.
Replacements which are under development for batteries in electric vehicles, or as a supplement to the batteries in such vehicles, are fuel cells which convert chemical fuel into electricity, flywheels which store energy in a spinning rotor, and ultra-capacitors which are capable of storing large amounts of electricity and which can be charged and discharged quickly.
Even though flywheels and ultra-capacitors used in conjunction with batteries can improve the efficiency of electric vehicles, the most optimistic projections which presently are available do not compare with the enormous amount of energy which is stored in a tank of gasoline. As a result, many researchers believe that the most popular electric drive vehicles in the future will be hybrids. Such hybrid vehicles are propelled by electric motors; but the electricity ultimately is obtained by small internal combustion engines that charge batteries, capacitors, rev up flywheels, or other power sources. For typical highway driving, only a relatively small amount of electrical energy is required; so that the internal combustion energy used to charge the batteries can be quite small. The storage cells then are charged during periods of low output, and are discharged rapidly when acceleration, steep hill climbing or other requirements are present.
Flywheels, used as energy storage devices, were first used in transportation applications in the 1950's. Flywheel powered buses were developed; and the flywheel rotors were revved up or accelerated at every stop. Composite rotors currently have been developed which can spin at very high revolutions (100,000 revolutions per second); and the speed is limited only by the tensile strength of the rim of the rotor. By using magnetic bearings, the friction on the axis of the rotor can be reduced sufficiently so that such rotors are capable of maintaining a major percentage of energy for several days.
Ultra-capacitors have been developed, primarily in conjunction with space applications and missile applications. These capacitors utilize manufacturing techniques which eliminate minuscule imperfections in the insulating film of capacitors which allows charges to leak away. The new materials make it possible to interleave the capacitor's dielectric and conductive plates extremely closely. As a result, ultra-capacitors have been developed which are capable of storing large amounts of energy in a relatively small volume. Such capacitors presently are available for use in calculators, watches, and electric razors.
One type of ultra-capacitor and its method of manufacture for a high energy density capacitor is disclosed in the United States patent to Baldwin U.S. Pat. No. 4,870,538. This capacitor is constructed of ceramic material interleaved with electrically conductive leads in a compact array which is capable of delivering its stored energy in extremely short discharge times, and providing high energy electrical pulses with extremely short rise times.
In the early 1800's Michael Faraday devised a machine called a homopolar generator. Such a generator consisted of a conducting disk rotating in an axial magnetic field. This machine was then operated as a generator with sliding brushes extracting current resulting from the voltage induced between the inner and outer regions of the disk when the rotational energy was supplied by an external driving source. The device also could be used as a motor when an external voltage was applied between the sliding brushes. A variation of this type of generator has been devised in the form of a hollow cylindrical dielectric, which is inserted into a stationary uncharged cylindrical capacitor (namely, an internal conductor and an external conductor surrounding the dielectric). When a uniform magnetic field was applied along the axis of this structure, the capacitor became charged as when the dielectric was rotated. This also is a homopolar effect, illustrating the effect of the static charge that is developed in the rotating dielectric. Widespread practical applications of this phenomenon, however, do not exist.
Three recent patents directed to variations of homopolar machines are the United States patents to Weldon U.S. Pat. No. 5,530,309, Kambe U.S. Pat. No. 5,481,149 and Hathaway U.S. Pat. No. 5,587,618. All three of these patents utilize the homopolar machine concept for use as a generator for producing high current, low voltage energy for various applications. The devices disclosed in these patents are bulky and not suitable for combination with battery storage cells used in conjunction with powering an electric vehicle.
It is desirable to provide a power generator which is suitable for use in conjunction with storage batteries for an electric car, and which employs homopolar effects to produce a charge on a capacitor in a manner which is efficient, compact and simple in construction.